This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-336082, filed Nov. 26, 1999; and No. 2000-180450, filed Jun. 15, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to a catheter for performing a diagnosis or a treatment of, for example, a blood vessel for carrying out various treatments and to a dilatation catheter for dilating the stenosis within the blood vessel so as to improve the blood flow on the side of the periphery of the stenosis for curing the stenosis.
The advent of a microcatheter has made it possible to perform therapy and diagnosis within a fine blood vessel or vasalium, though the conventional catheter is said to be incapable of performing such a therapy and diagnosis. The microcatheter includes, for example, a percutaneous transluminal coronary angioplasty catheter, hereinafter referred to as a dilatation catheter, used for curing the myocardial infarction or angina pectris. During the angioplasty, it is necessary to exchange the catheter in some cases. For example, it is necessary to exchange the catheter for change of the balloon size, for diagnosis of a region near the stenosis, and for replace of a therapy tool. The method of exchanging the catheter includes a method of using a long exchange guide wire. However, the long exchange guide wire is awkward because it takes time for handling the long wire and at least two operators are required. To overcome this difficulty, used is a xe2x80x9crapid exchangexe2x80x9d type catheter. The catheter of this type is constructed such that the distal end portion alone of the catheter tracks the guide wire.
Specifically, a rapid exchange type catheter disclosed in EP 925801A will be described. The catheter is constructed such that a coil assembly comprising a coil and a transition tube covering the coil is provided between a metal tube or a proximal shaft made of a material having a high strength substantially equal to that of the metal tube and a distal shaft made of a resin having a high flexibility so as to moderate a sudden change in rigidity between the proximal shaft of a high strength and the distal shaft of a high flexibility.
In the catheter, however, a clearance is inevitably formed between the proximal shaft and the coil arranged on the distal end side, with the result that the mechanical strength is lowered in the clearance portion, i.e., the portion where the transition tube alone is present. As a result, a problem is generated that the catheter tends to be broken in this portion and the catheter is deteriorated in terms of the pressure resistance. On the other hand, as a method that does not bring about such a clearance portion, it is conceivable to arrange the proximal shaft in a manner to extend into the coil so as to engage the both members, thereby improving the mechanical strength. In this case, however, it is inevitable for the engaged portion between the both members to be enlarged, which is undesirable.
An object of the present invention is provide a rapid exchange type catheter, which permits moderating a sudden change in rigidity between the proximal shaft having a high rigidity and the distal shaft having a flexibility, which is unlikely to be broken over the entire length, and which is excellent in pressure resistance.
According to a first aspect of the present invention, there is provided a dilatation catheter, comprising a tubular proximal shaft having relatively high rigidity; a tubular distal shaft having rigidity lower than that of the proximal shaft; a tubular intermediate section interposed between the proximal shaft and the distal shaft for connecting liquid tightly these shafts; a hub mounted on a proximal end portion of the proximal shaft, to which a pressure applying apparatus can be attached; a balloon arranged to a distal end portion of the distal shaft so as to be in fluid communication with the distal shaft, to which pressure can be applied from the hub; and a guide wire lumen having a distal aperture positioned on a distal end side to the distal end of the balloon and a proximal aperture positioned on a proximal end side to the proximal end of the balloon and on a distal end side to the proximal shaft, wherein a distal end portion of the proximal shaft is inserted into the intermediate section to form an insertion portion, the insertion portion having a spiral slit.
According to a second aspect of the present invention, there is provided a catheter, comprising a tubular proximal shaft having relatively high rigidity; a tubular distal shaft having rigidity lower than that of the proximal shaft; a tubular intermediate section interposed between the proximal shaft and the distal shaft for connecting liquid tightly these shafts; a hub mounted on a proximal end portion of the proximal shaft; a treatment device (device for therapy or diagnose, such as an ultrasonic diagnostic device, a laser, an atherectomy cutter, a medicine supply device, a radio frequency generator or an ultrasonic therapy device) arranged to a distal end portion of the distal shaft; and a guide wire lumen having a distal aperture positioned on a distal end side to the treatment device and a proximal aperture positioned on a proximal end side to the treatment device and on a distal end side to the proximal shaft, wherein a distal end portion of the proximal shaft is inserted into the intermediate section to form an insertion portion, the insertion portion having a spiral slit.
In the present invention, a spiral slit is formed on the proximal shaft, and the distal end portion of the proximal shaft is inserted into the intermediate section to form an insertion portion. As a result, it is possible to change gradually the rigidity of the catheter along the longitudinal direction of the catheter over the proximal shaft, the intermediate section, and the distal shaft.
According to the present invention, it is possible to arrange a reinforcing member on the distal end side relatively to the distal end of the proximal shaft in a manner to extend to reach at least the proximal aperture of the guide wire lumen.
In the present invention, in order to permit the rigidity of the shaft to be changed gradually, it is desirable to form the proximal aperture of the guide wire lumen in the intermediate section and to make the insertion portion of the proximal shaft extend to a region in the vicinity of the proximal aperture of the guide wire lumen.
To be more specific, it is desirable for the distance between the proximal aperture of the guide wire lumen and the distal end of the proximal shaft to be at most 5 mm. Further, in view of the case where the proximal aperture extends over a predetermined length along the longitudinal direction of the catheter, it is desirable for the distance between the distal end of the proximal aperture and the distal end of the proximal shaft to be at most 5 mm.
If the distance between the distal end of the proximal shaft and the proximal aperture of the guide wire lumen, preferably the distance between the distal end of the proximal shaft and the distal end of the proximal aperture of the guide wire lumen having a predetermined length, is set to fall within a range of between 0 and 5 mm, the catheter can exhibit a sufficient mechanical strength and a sufficient pressure resistance in the portion corresponding to the proximal aperture or the portion between the proximal aperture and the distal end of the proximal shaft even if a reinforcing member is not arranged in any of these portions. It follows that it is possible to prevent effectively the kink generation during the operation of the catheter.
In the present invention, it is desirable for the distal end of the spiral slit to be positioned on a portion within 10 mm from the distal end of the proximal shaft toward the proximal end.
In the present invention, it is desirable for the proximal shaft having relatively high rigidity to be formed of a metal tube. For applying a spiral slit processing to the distal end portion of the proximal shaft, it is possible to employ a general technique including, for example, a laser (e.g., YAG laser) processing, a discharge processing, a chemical etching or a cutting process. It is possible to make the pitch of the spiral slit shorter on the distal end side and longer on the proximal end side so as to permit the rigidity of the resultant insertion portion of the proximal shaft to be changed moderately from the proximal end side to the distal end side.
In the catheter of the present invention, it suffices to apply a spiral slit processing to the distal end portion of the proximal shaft. Therefore, it is possible to assemble the catheter without complicated steps. In addition, the insertion portion of the proximal shaft effectively prevents the kink generation. Also, the pitch of the spiral slit is made shorter on the distal end side and longer on the proximal end side so as to permit the rigidity of the insertion portion of the proximal shaft to be changed moderately from the proximal end side to the distal end side. It follows that the kink generation can be prevented more effectively.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.